For an indelible experience, stick your nose in a bottle of fish sauce—the whiff of fermented fish isn’t one you’re likely to forget. But don’t let the odor scare you. Known as nam pla (nahm PLAH) in Thailand, and nuoc nam (noo-AHK NAHM) in Vietnam, fish sauce is as crucial to the cuisine of Southeast Asia as soy sauce is to Chinese, responsible for the haunting salty flavors of dishes like Pad Thai.

Fish sauce is made by fermenting small, whole fish in vats of salty brine, drawing off the liquid, then aging it to the desired mellowness. The concept isn’t exclusive to Southeast Asia. Ancient Romans produced a similar condiment called garum—in southern Spain, ruins of garum factories date back to the Roman Empire. In a further historical twist, the condiment that reigns over every burger joint in America traces its roots to fish sauce. The word “ketchup” comes from the Chinese kêtsaip, a fish sauce that Dutch traders introduced to the West and which later inspired the tomato-based derivative.

Experiment with fish sauce by swapping it for soy sauce, but go easy as a little goes a long way. Create an Asian dipping sauce by mixing fish sauce with red pepper flakes and lime juice, or make an Asian-style broth by seasoning chicken stock with ginger, garlic and fish sauce. Fish sauce is an easy way to create umami, that sought-after savory “fifth taste,” and some cooks keep it by the stove, adding just a drop or two to bring a subtle depth to all-American gravies, stews and soups.